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Thread: why p''=pp' ??

  1. #1
    MHF Contributor
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    why p''=pp' ??

    i have a function
    y(x)

    i want to substitute by variable p.

    p=y'(x)=dy/dx

    every derivative is by dx because its the smallest variable
    so why

    why dp/dy=p'


    i cant see the meaning of derivative by y

    ??
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  2. #2
    Grand Panjandrum
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    Quote Originally Posted by transgalactic View Post
    i have a function
    y(x)

    i want to substitute by variable p.

    p=y'(x)=dy/dx

    every derivative is by dx because its the smallest variable
    so why

    why dp/dy=p'


    i cant see the meaning of derivative by y

    ??
    I don't see what you question is, but as a dash denotes differentiation by $\displaystyle x$:

    $\displaystyle
    \frac{dp}{dy}=\frac{dp}{dx}\frac{dy}{dx}=p'p
    $

    CB
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  3. #3
    MHF Contributor
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    why we are doig a derivative by y

    ??

    x is the smallest variable
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  4. #4
    Grand Panjandrum
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    Quote Originally Posted by transgalactic View Post
    why we are doig a derivative by y

    ??

    x is the smallest variable
    x being the "smallest" variable makes no sense.

    What is your actual question?

    CB
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